Really a great book recommend it for all interested in learning Silverlight via C#. No prior knowledge required except the basics of C# as a language.
Before choosing this book I've gone through lots of similar books and compared them all together, that one was the best by user comments, ratings, reviews, and by its selling rank.
Matthew McDonald is a great author of these books. I have read a number of his and I really like them. This book was my go-to reference for over a year. I think it is also on google books. When you need to find out the approved way to implement some technique, then the answer is probably in this book.
Well-written and explained. No prior knowledge of Silverlight is required, however, it is recommended to accompany this book with "Beginning Silverlight 4 in C#", written by the same author for absolute beginner.